Organisms develop from reproductive cells in precisely organized patterns that are controlled by complex cellular mechanisms. Many of these mechanisms are conserved throughout higher eukaryotes. Reproductive cells are a type of stem cell that has the unique ability to divide to produce more stem cells or to divide and differentiate into a complete organism. The mechanisms regulating stem cell maintenance are not well understood, and they are important because stem cells have the potential to treat human diseases such as Parkinson's disease. This project involves a study of the regulation of stem cell proliferation in a model organism, the nematode C. elegans. These animals have a gonad containing stem cells, and the focus of this project is to determine the function of a specific protein controlling proliferation of these cells called RNA Helicase A (RHA-1). Helicases use energy from ATP hydrolysis to separate duplex nucleic acids into single strands, and RNA helicases are involved in various steps of mRNA metabolism, such as transcription and splicing. RNA helicase A is essential for proper development in mice, flies, and the model organism C. elegans. Experiments performed thus far demonstrate that RHA-1 is required for germline proliferation, but the mechanism by which RHA-1 controls proliferation is not known. A comparison of the phenotype of worms containing a large deletion in the rha-1 gene with the phenotype of other mutant worms with germline defects suggests that RHA-1 may act by controlling transcription or by participating in a signaling pathway in the germline. In this proposal, genetic and molecular biology experiments are presented to test whether RHA-1 has one of these functions or a different function. The biochemical activities of RHA-1 have not been determined, and these activities are presumably required for its role in germline proliferation. Thus, experiments are described to determine the biochemical activities of RHA-1 that are required for it to work properly. The regulation of cell division in the germline is also related to cancer treatment, since many processes controlling cell division are conserved, and these processes become disrupted in cancerous cells. The ultimate goal of this project is to determine how transcription and other cellular processes affect development in all eukaryotes, including humans.